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    Copyright
    Praise for The Linux Programming Interface
    Dedication
    Preface
    Ch. 1. History and Standards
    Ch. 2. Fundamental Concepts
    Ch. 3. System Programming Concepts
    Ch. 4. File I/O: The Universal I/O Model
    Ch. 5. File I/O: Further Details
    Ch. 6. Processes
    Ch. 7. Memory Allocation
    Ch. 8. Users and Groups
    Ch. 9. Process Credentials
    Ch. 10. Time
    Ch. 11. System Limits and Options
    Ch. 12. System and Process Information
    Ch. 13. File I/O Buffering
    Ch. 14. File Systems
    Ch. 15. File Attributes
    Ch. 16. Extended Attributes
    Ch. 17. Access Control Lists
    Ch. 18. Directories and Links
    Ch. 19. Monitoring File Events
    Ch. 20. Signals: Fundamental Concepts
    Ch. 21. Signals: Signal Handlers
    Ch. 22. Signals: Advanced Features
    Ch. 23. Timers and Sleeping
    Ch. 24. Process Creation
    Ch. 25. Process Termination
    Ch. 26. Monitoring Child Processes
    Ch. 27. Program Execution
    Ch. 28. Process Creation and Program Execution in More Detail
    Ch. 29. Threads: Introduction
    Ch. 30. Threads: Thread Synchronization
    Ch. 31. Threads: Thread Safety and Per-Thread Storage
    Ch. 32. Threads: Thread Cancellation
    Ch. 33. Threads: Further Details
    Ch. 34. Process Groups, Sessions, and Job Control
    Ch. 35. Process Priorities and Scheduling
    Ch. 36. Process Resources
    Ch. 37. Daemons
    Ch. 38. Writing Secure Privileged Programs
    Is a Set-User-ID or Set-Group-ID Program Required?
    Operate with Least Privilege
    Be Careful When Executing a Program
    Avoid Exposing Sensitive Information
    Confine the Process
    Beware of Signals and Race Conditions
    Pitfalls When Performing File Operations and File I/O
    Don't Trust Inputs or the Environment
    Beware of Buffer Overruns
    Beware of Denial-of-Service Attacks
    Check Return Statuses and Fail Safely
    Summary
    Exercises
    Ch. 39. Capabilities
    Ch. 40. Login Accounting
    Ch. 41. Fundamentals of Shared Libraries
    Ch. 42. Advanced Features of Shared Libraries
    Ch. 43. Interprocess Communication Overview
    Ch. 44. Pipes and FIFOs
    Ch. 45. Introduction to System V IPC
    Ch. 46. System V Message Queues
    Ch. 47. System V Semaphores
    Ch. 48. System V Shared Memory
    Ch. 49. Memory Mappings
    Ch. 50. Virtual Memory Operations
    Ch. 51. Introduction to POSIX IPC
    Ch. 52. POSIX Message Queues
    Ch. 53. POSIX Semaphores
    Ch. 54. POSIX Shared Memory
    Ch. 55. File Locking
    Ch. 56. Sockets: Introduction
    Ch. 57. Sockets: UNIX Domain
    Ch. 58. Sockets: Fundamentals of TCP/IP Networks
    Ch. 59. Sockets: Internet Domains
    Ch. 60. Sockets: Server Design
    Ch. 61. Sockets: Advanced Topics
    Ch. 62. Terminals
    Ch. 63. Alternative I/O Models
    Ch. 64. Pseudoterminals
    Appx. A. Tracing System Calls
    Appx. B. Parsing Command-Line Options
    Appx. C. Casting the NULL Pointer
    Appx. D. Kernel Configuration
    Appx. E. Further Sources of Information
    Appx. F. Solutions to Selected Exercises
    Bibliography
    Appx. G. Updates
    Colophon
    Index
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    Chapter 38. Writing Secure Privileged Pr... > Don't Trust Inputs or the Environmen...

    38.8. Don't Trust Inputs or the Environment

    Privileged programs should avoid making assumptions about the input they are given, or the environment in which they are running.

    38.8.1.

    38.8.1.1. Don't trust the environment list

    Set-user-ID and set-group-ID programs should not assume that the values of environment variables are reliable. Two variables that are particularly relevant are PATH and IFS.


      

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